This invention relates to the art of windmills and wind machines in which a multiblade fan or rotor drives a transmission that converts rotary motion to reciprocation motion to raise and lower a vertical rod driving a water pump or other load. In this type of wind machine, the rotor and transmission are mounted on a high tower and lift the rod, pump cylinder and water only on the up stroke of the rod. On the down stroke the water does not move, but the rod and pump cylinder move down. Thus useful work is done only on the upward or lift stroke. The load is not driven on the down stroke.
Conventional windmills suffer a major limitation in that they do not operate at wind velocities below 15 miles per hour. Since wind velocities equal to or greater than 15 miles per hour occur over the earth's surface only about 30% of the time, the windmills are effective less than one-third of the time, even though their use may be required 100% of the time. When the wind falls below 15 miles per hour momentarily, the momentum of the rotor is usually insufficient to drive the rotor around until sufficient wind velocity returns, so that the rotor stops and may require wind velocity greater than 15 miles per hour to start it again. If such a high velocity wind gust does not occur the windmill remains inactive.
Attempts have been made heretofore to improve the lifting ability of the multiblade, pumping type of windmill by counterbalancing the weight of the lift rod and water by using pulleys and weights. These have not proven practical and reliable in operation. Another proposed counterbalancing arrangement has been proposed in U.S. Pat. No. 3,782,222, issued Jan. 1, 1974. This patent describes a counterbalancing assembly in which telescopic arms extend outwardly from opposite sides of a vertically reciprocating lift rod in a windmill. The arms are secured pivotally to rotatable discs carried by the windmill tower. Each disc has a flexible cable connected between the reciprocating vertical rod and disc to counterbalance the weight of the rod. The arms have telescopic sections which can be extended or retracted to vary the arm's length and thereby to adjust the leverage exerted by the assembly on the rod. This type of counterbalance assembly is generally capable of counterbalancing about 98% of the weight of the reciprocating rod and extends the operability of a windmill in which it is installed to wind velocities as low as 3 miles per hour. In theory, this type of counterbalance system should be adjustable to counterbalance the weight of the rod and at least part of the weight of liquid being pumped to assist the rotor during the lifting part of the cycle. However, when the rod is being lowered, the rotor must provide power to raise the heavy telescopic arms. Conventional windmills are not designed to push a load during the down part of the cycle. If they are required to push down a rod and attached pump cylinder, the transmission comes away from or lifts off its mounting on the tower, the gearing jams, and the windmill becomes inoperative. Difficult and time consuming repairs may then be necessary to repair the windmill to get it operating again. This inability of conventional windmills to pump or push on the down part of the cycle of operation is characteristic of all the more than 6,000,000 windmills heretofore erected. That is why windmills are used only for lifting loads, not for pushing them down. Thus the counterbalance system employing telescopic arms, rotating discs and connecting cables, in practice, cannot be used to assist in lifting the water being pumped, and is limited to assisting in lifting the rod and pump cylinder alone. This counterbalance system having telescopic arms has a number of further limitations which limit its general use. One is the difficulty or impossibility of accurate adjustment in the field of the lengths of the telescopic arms to insure that they are both equal in length and precisely set so as to counterbalance only the weight of the rod and pump cylinder and not more than this weight. Otherwise the transmission motion is opposed, the telescopic arms flap and the connecting cables break. If less than the weight of the rod and cylinder is counterbalanced, the effectiveness of counterbalancing is reduced and the windmill cannot operate efficiently at low wind velocities. Furthermore, the setting of the telescopic arms frequently comes out of adjustment because holding screws loosen and the arm sections slide with respect to each other, so that the arm lengths must be reset. When this occurs during windmill operation, the windmill stops operating or must be stopped, and difficult field adjustments of the telescopic arms must be made. This is often a time consuming operation, during which the windmill cannot operate.